Viral Inhibitors of Biological Origin. II. A Viral Inhibitory Factor Obtained from E. coli 0111 and Inhibition of Viral Replication by Nucleic Acid Derivatives. ∗

Suppression of viral multiplication by crude materials derived from a variety of sonically disrupted bacteria has been described (1,2). The inhibitory material from each bacterial species tested suppressed certain viruses without affecting the multiplication of others. Thus, while arboviruses are inhibited by material derived from an unclassified Coryne-bacterium, ECHO 11 is suppressed by material from Corynebacterium diphtheriae (both non-toxigenic and intermedius strains) and vaccinia is suppressed by material derived from various Escherichia coli serotypes and Salmonella typhimurium. The present report is concerned with further characterization of the material from E. coli 0111, using the multiplication of vaccinia virus in primary human amnion cell cultures as an indicator system. Preliminary observations concerning viral inhibition by nucleic acid derivatives are also included in this report.

Preparation. An inoculum of E. coli 0111, obtained from Dr. J. G. Michael, was grown in one liter of Bacto nutrient broth for 18 hours. The entire culture was used to prime a Biogen containing 40 liters of medium consisting of 7 g K₂HPO₄, 3 g KH₂PO₄, 0.5 g sodium citrate. 2 H₂O, 1 g (NH₄)₂SO₄, 0.12 g MgSO₄, and 5 g glucose in each liter of water. After 24 hours'growth at 37°C the culture was centrifuged and dried at room temperature. Sixty g of dried E. coli 0111 were obtained in this manner. Acetone soluble substances were removed from the dried culture by 3 extractions with 600 ml of acetone. Following this the bacteria were redried at room temperature. The acetone extracted bacteria were taken up in 100 ml of water and the insoluble residue was discarded. The water soluble material was dialyzed against running tap water for 24 hours. The dialysand was concentrated by lyophilization and then dissolved in 100 ml of distilled water.